Zum Einfluß der Feuchte auf die Schlupfrate und Entwicklungsdauer der Eier mitteleuropäischer Feldheuschrecken (Orthoptera, Acrididae)

Abstract

Eggs of 12 Central European grasshopper species were incubated under different moisture conditions. These ranged from flooded eggs down to 30% RH. Three series of experiments were carried out: 1. To test the moisture requirement and resistance to drought before and after the winter period, 2. to test only the drought resistance after overwintering, and 3. to test drought resistance before overwintering. During the winter period all eggs were kept uniformly in contact with water. For each species the number of hoppers hatching under the different moisture conditions are presented as well as the number of days required for the eggs to hatch at 24 °C, counting only the time after the winter period. The occurence of Acrididae in specific habitats rests partly on the effect of moisture on egg development. The species differ with regard to the drought resistance of their eggs, expressed as the number of larvae hatching at different humidities. This is correlated with the place of oviposition (above or below ground) and with the typical microclimate of the species habitats. The time needed to hatch varies considerably between species and also within species when the eggs are kept at different humidities. The hatching sequence of the species under suitable conditions in the laboratory is comparable with that in nature. When contact water is lacking hatching occurs later. This retardation in development is more expressed in species with low drought resistance in the egg stage. Leaving the eggs inside the pods does not reduce the number of hatchlings except when there is no contact water or when the pods are flooded. However, hatching occurs later in species with hard egg pods.